Modern chemical (including biochemical) practice includes numerous techniques for treating a liquid sample: mixing, reacting, filtering, dialyzing, synthesizing, fractionating, detecting, catalyzing (including enzymatically catalyzing) reactions, performing various separations, and the like.
For example, it may be desirable to remove solvent from a liquid sample in order to concentrate one or more solutes so that they may be analyzed, detected, further treated, etc. It also may be desirable to remove solutes, including macromolecular solutes or low molecular weight ions, each of which may interfere with analysis, detection or further treatment of one or more solutes of interest. This may be particularly so in biochemical practice, where complex mixtures of biological molecules can be obtained from living organisms, especially when the presence of a particular chemical species may interfere with the detection, analysis or further treatment of other solutes in the mixture.
Standard chromatographic techniques may be useful for performing many types of chemical separations. In addition, modified chromatographic methods in which a sorptive or reactive medium is cast in-place in a structure such as a pipette tip may be used to perform chemical separations on microliter-volume samples. In contrast to standard chromatographic methods, such modified, microliter-volume chromatographic methods can include a device that permits a sample to be subjected to multiple passes through the sorptive or reactive medium, thereby allowing multiple opportunities for the chemical separation to progress so long as the sample does not saturate the sorptive or reactive capacity of the medium. However, such devices may not be convenient for chemical separations in samples of larger volumes, e.g., milliliter or multiple-milliliter volumes.
Certain chromatography systems include a plurality of pumps to supply solvent to a plurality of chromatography columns. Each pump includes a chamber with a movable piston, an inflow valve and an outflow valve. Withdrawing the pistons from the chambers generates a vacuum in each chamber that draws solvent through the inflow valve and into the chamber. When the desired delivery volume of solvent has been drawn into each chamber, the pistons may be pushed back into the chambers, thereby forcing the solvent through the outflow valve and into the chromatography column. The pistons may be driven in concert using a pneumatic or hydraulic system.
Some devices designed for continuous chromatography have been adapted to be useful for the purpose of treating a liquid sample by depleting one or more undesirable chemical species. In such adaptations, the chromatography column is replaced by an element containing a substance selected to perform the desired depletion treatment, such as a functionalized solid support. The samples requiring treatment may be introduced into the buffer stream, thereby allowing the chemical species that are to be depleted from the sample to interact with the depletion element. Such devices may have at least two reservoirs, one for carrying the liquid sample, and a second for generating the column. In such devices, a second buffer can be used to elute the separated species from the depletion element so that the depletion element may be used to treat one or more subsequent samples.
Alternatively, certain batch processes are known for depleting an undesirable chemical species from a liquid sample. In such processes, a small chamber may include an article that contains a depletion substance selected to perform the desired depletion, i.e., removal of at least a portion of an undesirable chemical species from the liquid sample. A sample may be flushed through the chamber using, for example, low speed centrifugation or syringe plunger pressure, thereby allowing the depletion substance to remove the undesirable chemical species from the sample. For complete depletion, it may be necessary to pass the sample through the depletion substance more than once, thus requiring the operator to collect the partially depleted sample and recycle it through the process.
Certain other devices are designed for extraction of nucleic acids from a sample without pipetting. The sample and a lysis buffer are predispensed in vessels such as syringes that are interconnected through a narrow passage. The sample and lysis buffer can be mixed by transferring the sample and buffer mixture back and forth from one vessel to the other. One of the vessels can contain, for example, an extraction matrix for extracting nucleic acids from the sample and buffer mixture. Repeated transfer of the mixture ensures thorough mixing and offers multiple opportunities for nucleic acids to be extracted from the mixture by the matrix.
The utility of many chromatography-based devices and procedures may be limited; such devices may not be suitable for performing chemical syntheses, high-throughput analyses, or processing sequences involving multiple buffers, solutions and/or reagent in an automated manner, and the separated chemical species may be eluted in relatively large volumes of elution buffer, necessitating a concentration step before the eluted chemical species may be used for subsequent analysis or further treatment.
Many standard procedures exist for detection and analysis of one or more particular chemical species in a liquid sample. In many cases, such processes require that the sample be subjected to certain preparatory steps prior to the actual detection or analytical steps. In some cases, the sample preparation may be labor-intensive. Also, in some cases, the sample preparation may be incompatible with the detection or analytical method, e.g., the pH of buffers used in sample preparation and the analytical method may be different and incompatible. In such cases, it may be necessary to manually adjust one or more chemical properties of the prepared sample (e.g., pH, concentration, etc.) prior to performing the desired detection or analytical test. Consequently, efficiency of the overall process may be reduced, even to the point that the devices and processes being used may become unsuited for high-throughput analysis of the samples.
Therefore, a need exists for a device that may be employed in order to subject a liquid sample to one or more of a broad range of chemical treatments. Furthermore, a need exists for such a device that may be automated or is otherwise suitable for use in high-throughput analyses.